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| United States Patent |
6,015,596
|
|
Miwa
, et al.
|
January 18, 2000
|
Fluorine-containing silicon network polymer, insulating coating thereof,
and electronic devices therewith
Abstract
A fluorosilicon network polymer prepared by the reaction of a
tetraholosilane of the formula 1: SiX4 with an organohologen compound of
the formula 2: RZ , an insulating coating prepared therefrom,
semiconductor devices coated therewith, and processes for producing the
same. In said formulas, R represents at least monofluorinated alkyl or
aryl; and X and Z represent each independently boromine, iodine or
chlorine.
| Inventors:
|
Miwa; Takao (Hitachinaka, JP);
Watanabe; Akira (Sendai, JP);
Ito; Osamu (Sendai, JP);
Matsuda; Minoru (Sendai, JP)
|
| Assignee:
|
Hitachi, Ltd. (Tokyo, JP)
|
| Appl. No.:
|
945472 |
| Filed:
|
October 27, 1997 |
| PCT Filed:
|
April 24, 1996
|
| PCT NO:
|
PCT/JP96/01107
|
| 371 Date:
|
October 27, 1997
|
| 102(e) Date:
|
October 27, 1997
|
| PCT PUB.NO.:
|
WO96/34034 |
| PCT PUB. Date:
|
October 31, 1996 |
Foreign Application Priority Data
| Apr 25, 1995[JP] | 7-099228 |
| Jul 18, 1995[JP] | 7-181416 |
| Current U.S. Class: |
427/489; 205/414; 205/420; 257/E21.26; 257/E21.276; 427/376.2; 501/88; 522/148; 528/10; 528/25; 528/39; 528/42 |
| Intern'l Class: |
C08J 007/18 |
| Field of Search: |
205/414,420
528/25,39,10,42
501/88
522/148
427/489,376.2
|
References Cited
U.S. Patent Documents
| 4808685 | Feb., 1989 | Bortolin | 528/10.
|
| 4826892 | May., 1989 | Shimada et al. | 528/10.
|
| 4841083 | Jun., 1989 | Nagai et al. | 528/10.
|
Other References
Concise Encyclopedia of Polymer Science and Engineering (1990 ed). p. 644.
|
Primary Examiner: Marquis; Melvyn I.
Attorney, Agent or Firm: Antonelli, Terry, Stout & Kraus, LLP
Claims
We claim:
1. A fluorine-containing silicon network polymer represented by the
following general formula:
##STR4##
where, R is an aromatic group or alkyl group containing at least one
fluorine, and n is an integer, the polymer having a molecular weight of
1,000 to 100,000.
2. a fluorine-containing silicon network polymer consisting of the reaction
product of tetrahalosilane of chemical formula 1 and organohalogenide of
chemical formula 2:
SiX.sub.4 ( 1)
RZ (2)
where, R is an aromatic group or alkyl group containing at least one
fluorine, X is selected from the group consisting of bromine, iodine and
chlorine, Z is selected from the group consisting of bromine, iodine and
chlorine, and X and Z can be different materials from each other.
3. An insulating film comprised of fluorine-containing silicon network
polymer represented by the following general formula:
##STR5##
where, R is an aromatic group or alkyl group containing at least one
fluorine, and n is an integer, said polymer having a molecular weight of
1,000 to 100,000.
4. An insulating film comprised of fluorine-containing silicon network
polymer consisting of the reaction product of tetrahalosilane of chemical
formula 1 and organohalogenide of chemical formula 2:
SiX.sub.4 ( 1)
RZ (2)
where, R is an aromatic group or alkyl group containing at least one
fluorine, X is selected from the group consisting of bromine, iodine and
chlorine, Z is selected from the group consisting of bromine, iodine and
chlorine, and X and Z an be different materials from each other.
5. An insulating film comprised of fluorine-containing silicon network
polymer according to claim 3 or 4, wherein said insulating film is one
that electromagnetic waves are irradiated in the presence of oxygen.
6. A method of manufacturing fluorine containing silicon network polymer
comprising the steps of:
inserting a pair of electrodes one of which is a magnesium electrode into
mixed solution of tetrahalosilane of chemical formula 1 and
organohalogenide of chemical formula 2:
SiX.sub.4 ( 1)
RZ (2)
where, R is an aromatic group or alkyl group containing at least one
fluorine, X is selected from the group consisting of bromine, iodine and
chlorine, Z is selected from the group consisting of bromine, iodine and
chlorine, and X and Z can be different materials from each other,
applying a voltage across said pair of electrodes to react the
tetrahalosilane and the organohalogenide, so as to form a reacted
solution, and
coating the reacted solution on a substrate to form a thin film.
7. A method of manufacturing fluorine containing silicon network polymer
according to claim 6, wherein the thin film is thermally treated at
200.degree. C. to 1,000.degree. C. in the presence of oxygen.
8. A method of manufacturing fluorine containing silicon network polymer
according to claim 6, wherein electromagnetic waves are irradiated on the
thin film in the presence of oxygen.
9. A method of manufacturing fluorine containing silicon network polymer
according to claim 6, wherein electromagnetic waves are irradiated on the
thin film in the presence of oxygen, and then the thin film is thermally
treated at 200.degree. C. to 1,000.degree. C. in the presence of oxygen.
10. An electronic device, wherein an insulating layer of a circuit
substrate of said electronic device is configured with an insulating film
comprised of fluorine-containing silicon network polymer represented by
the following general formula:
##STR6##
where, R is an aromatic group or alkyl group containing at least one
fluorine, and n is an integer, the polymer having a molecular weight of
1,000 to 100,000.
11. A method of forming a thin film, wherein after forming a thin film of
silicon network polymer on a substrate at least one of the following steps
are carried out: (a) irradiating electromagnetic waves to the film of the
silicon network polymer in the presence of oxygen, and (b) thermally
treating the film of silicon network polymer at 200.degree. C. to
1,000.degree. C. in the presence of oxygen.
12. A method of forming a thin film which comprises the steps of: forming a
thin film of silicon network polymer on a substrate; irradiating
electromagnetic waves to the film of the silicon network polymer; and
thermally treating the film of silicon network polymer at 200.degree. C.
to 1000.degree. C.
13. A method of forming a thin film according to claim 11 or 12, wherein
the silicon network polymer is made by the polymerization of organic metal
compound represented by the following formulas 3 and/or 4,
##STR7##
Where, R.sub.1, R.sub.2, R.sub.3, are aromatic group, fluoroaliphatic
group, or aliphatic group in which the carbon number is equal to or less
than 10, and they may be different from one another or the same as each
other.
14. A method of forming a thin film according to claim 13, wherein the
silicon network polymer is made by reacting and polymerizing (1) organic
metal compound represented by the following formulas 3 and/or 4
##STR8##
where, R.sub.1, R.sub.2, R.sub.3 are aromatic group, fluoroaliphatic
group, or aliphatic group in which the carbon number is equal to or less
than 10, and they may be different from one another or the same as each
other, with (2) at least one of alloy of alkali metals, copper or
magnesium.
15. An electrically insulating thin film made by irradiating
electromagnetic waves to the film of the silicon network polymer in the
presence of oxygen, and thermally treating the thin film of silicon
network polymer at 200.degree. C. to 1000.degree. C. in the presence of
oxygen.
16. A method of forming an electrically insulating thin film which
comprises the steps of: forming a thin film of silicon network polymer on
a substrate, irradiating electromagnetic waves to the film of the silicon
network polymer in the presence of oxygen, and then thermally treating the
thin film of silicon network polymer at 200.degree. C. to 1,000.degree. C.
in the presence of oxygen.
17. A semiconductor device which uses an insulating layer as an inter-layer
insulating film, made by forming a thin film of silicon network polymer on
a substrate, irradiating electromagnetic waves to the film of the silicon
network polymer in the presence of oxygen, and then thermally treating the
thin film of silicon network polymer at 200.degree. C. to 1,000.degree. C.
in the presence of oxygen.
18. A method of manufacturing a semiconductor device which uses an
insulating layer as an inter-layer insulating film, made by forming a thin
film of silicon network polymer on a substrate, irradiating
electromagnetic waves to the thin film of the silicon network polymer in
the presence of oxygen, and then thermally treating the film of silicon
network polymer at 200.degree. C. to 1,000.degree. C. in the presence of
oxygen.
19. A semiconductor device comprising an insulating layer flattened by a
chemical machinery polishing method as an inter-layer insulating film, in
which the insulating layer is made by forming a thin film of silicon
network polymer on a substrate, irradiating electromagnetic waves to the
thin film of the silicon network polymer in the presence of oxygen, and
then thermally treating the thin film of silicon network polymer at
200.degree. C. to 1000.degree. C. in the presence of oxygen.
20. A method of manufacturing a semiconductor device which comprises a step
of flattening an insulating layer by a chemical machinery polishing
method, the insulating layer being made by irradiating electromagnetic
waves to the thin film of the silicon network polymer formed on a
substrate in the presence of oxygen, and then thermally treating the film
of silicon network polymer at 200.degree. C. to 1,000.degree. C. in the
presence of oxygen.
21. A semiconductor device which uses the insulating layer as a conductive
layer and/or a semi-conductive layer, made by forming a thin film of
silicon network polymer on a substrate, irradiating electromagnetic waves
to the film of the silicon network polymer in the presence of oxygen, and
then thermally treating the thin film of silicon network polymer at
200.degree. C. to 1000.degree. C. in the presence of oxygen.
22. A method of manufacturing a semiconductor device wherein the insulating
layer is used as a conductive layer and/or a semi-conductive layer, made
by forming a thin film of silicon network polymer on a substrate,
irradiating electromagnetic waves to the film of the silicon network
polymer in the presence of oxygen, and then thermally treating the thin
film of silicon network polymer at 200.degree. C. to 1000.degree. C. in
the presence of oxygen.
23. A fluorine-containing silicon network polymer according to claim 1 or
2, wherein said polymer is an amorphous fluorine-containing silicon
network polymer.
24. An insulating film according to claim 3 or 4, wherein said polymer is
an amorphous fluorine-containing silicon network polymer.
25. An electronic device according to claim 10, wherein said polymer is an
amorphous fluorine-containing silicon network polymer.
26. A method of forming a thin film according to claim 11 or 12, wherein
the silicon network polymer is a fluorine-containing silicon network
polymer.
27. A method of forming a thin film according to claim 13, wherein the
silicon network polymer is a fluorine-containing silicon network polymer.
28. A method of forming a thin film according to claim 14, wherein the
silicon network polymer is a fluorine-containing silicon network polymer.
29. An electrically insulating thin film according to claim 15, wherein the
silicon network polymer is a fluorine-containing silicon network polymer.
30. A method according to claim 16, wherein the silicon network polymer is
a fluorine-containing silicon network polymer.
31. A semiconductor device according to claim 17, 19 or 21, wherein the
silicon network polymer is a fluorine-containing silicon network polymer.
32. A method of manufacturing a semiconductor device according to claim 18,
20 or 22, wherein the silicon network polymer is a fluorine-containing
silicon network polymer.
Description
TECHNICAL FIELD
The present invention relates to silicon network polymer containing
fluorine in polymer structure, an insulating film and a manufacturing
method thereof. Further, the present invention relates to a method of
forming a thin film by a photolithography method, using silicon network
polymer containing fluorine in polymer structure.
BACKGROUND ART
In the Journal of The Japanese Society of Applied Physics, Volume 34, L452,
1995, there is disclosed silicon network polymer and the synthesizing
method thereof. The synthesizing method uses Wurtz's reaction in which
trihalosilane is condensation-reacted with sodium metal.
Further, in Japanese Patent Application Laid-Open No. 3-258834 (1991),
there is disclosed straight chain fluorine-containing polysilane and the
synthesizing method thereof. This also uses Wultz's reaction.
However, in the prior art, fluorine-containing silicon network polymer has
never been synthesized. The reason is that the compounds which can be used
for the Wurtz's reaction are limited, and in particular there is no raw
material for the fluorine-containing silicon network polymer.
In electronic devices, typically a semiconductor, it is extremely desired
to obtain an insulating layer with lower permittivity in order to improve
its performance. In order to respond the above-mentioned requirement,
there has been studied a plasma TEOS film by a CVD method, a SiOF film,
etc. However, in order to form those films, it is necessary to provide a
CVD equipment, and further the productivity is low. From such a point of
view, prior art uses a coating method to form the insulating layer.
In the Journals of The Japanese Society of Applied Physics, Volume 77, 2796
(1995) and Volume 34, L452 (1995), there are disclosed methods of forming
a SiO film by using silicon network polymer. However, because the silicon
network polymer containing no fluorine is used, it is impossible to obtain
the desired insulating layer with lower permittivity.
Further, because the stability of the straight chain fluorine-containing
polysilane is low, it is impossible to form the desired insulating layer
even if the methods disclosed in the Journals of Japanese Society of
Applied Physics, Volume 77, 2796 (1995) and Volume 34, L452 (1995) are
applied.
While organic spin-on-glass (hereinafter, abbreviated as SOG), one of
polysiloxane type coating material can provide the insulating layer with
relatively low permittivity, the stress is large when hardened. It is
impossible to form the desired insulating layer except the insulating
layer with thickness of sub-micron order. Further, the workability is low
and thus it is apt to crack.
As the semiconductor is highly integrated, the irradiation light of far
shorter wave is required for use of photolithography in order to obtain
fine wires. While in the photolithography g-line (436 nm), one of the
emission characteristics of a mercury lamp was commonly used, recently
i-line (365 nm) more suitable to fine working has become more used. The
fine working is carried out by using photo resist of which a major
component is organic macromolecules containing aromatic ring within its
molecules. In the development process of forming patterns, a wet
development method due to solvent or a dry etching method due to reactive
gas is used.
It seems that the microstructures of semiconductors will be further
improved. However, previously the photo resist of which a major component
is organic material is not suitable for the lithography which uses the
light with wavelength shorter than 350 nm in which it has the
self-absorption action against the wavelength shorter than 350 nm.
As main light sources of which the wavelength is equal to or less than 350
nm, there are far-ultraviolet or excimer laser such as KrF (248 nm) or Ar
(193 nm). The spotlight centers on the photolithography in which the
combination of the light source with short wavelength and polysilane of
which sensitivity falls within the short wavelength area are used.
However, a pattern forming method which uses these polysilane resist also
utilizes a wet development method or a dry etching method in which
reactive gas is used. (see SPIE, Vol.1466, P211 (1991))
Further, in order to form active elements such as transistors, diodes, etc.
on the substrate of a semiconductor, it is necessary to perform more
complicated processes such as oxidation reaction, impurity diffusion, ion
implantation, etc. in addition to the above-mentioned wiring forming
process.
In addition, in order to form light wave-guiding passage, etc., it is
necessary to pass through furthermore complicated processes such as
etching, coating, etc. Accordingly, there are many problems in the
efficiency of manufacturing, the yields, etc.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a new fluorine-containing
silicone network polymer, an insulating film of the polymer and a
manufacturing method thereof.
Another object of the present invention is to provide an electronic device
such as an integrated circuit which the insulating film of the polymer is
used, a semiconductor, etc. and a manufacturing method thereof.
Large amounts of organic solvent are used in the wet etching for the
pattern forming. Further, because the resolution at the edge of a pattern
is small, it is very difficult to form fine patterns. In addition, because
it is necessary to use special-purpose and expensive equipment in order to
perform the dry etching, the throughput is deteriorated.
Particularly with regard to the resist of which a major component is
polysilane, it is possible to perform the photo lithography by using the
short wave less than 350 nm. However, since large amounts of organic
solvent such as xylene or toluene are used in the wet-etching, and these
solvents are flammable and extremely poisonous, it is very difficult to
industrialize.
Further, As to materials of a silicone system, typically SiO.sub.2, it is
required to use, for example, CVD equipment to form an SiO.sub.2 film.
Therefore, there is a problem in productivity. In order to solve the
problem, it can use paint type materials of a siloxane system called
spin-on-glass (hereinafter, abbreviated as SOG). However, because with
regard to SOG, the stress when hardened is large, it is impossible to form
such a film with thickness more than a sub-micron order. Further, the SOG
is fragile and it is difficult to work the SOG.
Accordingly, a further object of the present invention is to provide a
pattern forming method in which it is possible to form a fine pattern with
efficiency and with safety, by using the shorter wave less than 350 nm.
A further object of the present invention is to provide a method of forming
a conductive (SiC), a semi-conductive (a-Si), a insulating (SiO), or a
light transmissive (SiO.sub.2) thin film, materials for an insulating film
of which the film characteristics and the workability are improved by
using the thin film forming method, a semiconductor device in which the
film materials are used, and a method thereof.
The above-mentioned problems are solved by using the following materials,
films, semiconductor devices and methods.
(1) A fluorine-containing silicon network polymer represented by the
following general formula, having molecular weight of 1,000 to 100,000.
##STR1##
(where, R is aromatic group or alkyl group containing at least one
fluorine, and n is integer.)
(2) A fluorine-containing silicon network polymer consisting of the
reactant of tetrahalosilane of chemical formula 1 and organohalogenide of
chemical formula 2.
SiX.sub.4 (1)
RZ (2)
(where, R is aromatic group or alkyl group containing at least one
fluorine, X is bromine, iodine, chlorine, Z is bromine, iodine, chlorine,
and X and Z can be different materials to each other.)
(3) An insulating film comprised of the fluorine-containing silicon network
polymer.
The fluorine-containing silicon network polymer can be obtained by
inserting a pair of electrodes one of which is a magnesium electrode into
mixed solution of the tetrahalosilane of chemical formula 1 and the
organohalogenide of chemical formula 2, applying a voltage between the
pair of electrodes to react, and coating the reacted solution on the
substrate to form a thin film.
It should be appreciated that the thin film can be thermally treated at
200.degree. C. to 1,000.degree. C., in the presence of oxygen.
Further, it should be appreciated that an electromagnetic wave can be
irradiated on the thin film in the presence of oxygen.
Furthermore, it should be appreciated that an electromagnetic wave can be
irradiated on the thin film in the presence of oxygen, and then the thin
film can be thermally treated at 200.degree. C. to 1,000.degree. C., in
the presence of oxygen.
It is possible directly to form the thin film on the electronic device by
coating.
The fluorine-containing silicon network polymer which has never been
obtained in the prior art can be obtained by reacting the tetrahalosilane
and the organohalogenide in the presence of the magnesium electrodes. The
insulating film with low permittivity and having the improved
characteristics can be provided by using the new polymer.
The advantages of the above reaction are in that the range of applications
of the reaction is very broad and the yield is very high.
Next, a synthetic method will be explained.
Firstly, organohalogenide reacted with fluorine is reacted with magnesium
to produce Grignard reagent. The produced Grignard reagent and
tetrahalosilane are reacted with each other to produce
trihaloorganosilane. Finally, the desired fluorosilicon network polymer is
obtained by the condensation of the triholoorganosilane. Accordingly,
instead of the above-mentioned fluoroorganohalogenide, it is possible to
use any materials which can produce Grignard reagent, such as
fluorohaloallyl, fluorohaloalkyl, etc.
Further, the yield of the produced polymer is higher than that due to the
Wurtz's reaction. An R content of the polymer can be adjusted by changing
the ratio of SiX.sub.4 to RZ.
The synthesis of polysilane having fluoroalkyl group is disclosed in
Japanese Patent Application Laid-Open No. 3-258834 (1991). However, it
relates to straight chain polysilane, and thus it is different from the
present invention.
By using the method described in the Journal of The Japan Society of
Applied Physics, Volume 77, 2796 (1995), it is possible to make an
oxidation film by the produced fluorosilicon network polymer and to
perform the patterning. The relative permittivity of the oxidation film
obtained is lower than that due to the conventional silicon network
polymer. It is, therefore, more advantageous to improve the performance of
electronic devices.
The film obtained by oxidizing the fluorosilicon network polymer is small
in film stress, and thus it is suitable to use as an insulating layer for
semiconductors.
(4) A method of forming a thin film wherein after forming a thin film of
silicon network polymer on a substrate at least one of the following steps
are carried out: (a) irradiating an electromagnetic wave to the film of
the silicon network polymer in the presence of oxygen, (b) thermally
treating the film of silicon network polymer at 200.degree. C. to
1,000.degree. C. in the presence of oxygen.
(5) A method of forming a thin film which comprises the steps of: forming a
thin film of silicon network polymer on a substrate; irradiating an
electromagnetic wave to the film of the silicon network polymer; thermally
treating the film of silicon network polymer at 200.degree. C. to
1,000.degree. C.
(6) A method of forming a thin film wherein the silicon network polymer is
made by the polymerization of organic metal compound represented by the
following formulas 3 and/or 4.
##STR2##
(Where, R.sub.1, R.sub.2, R.sub.3 are aromatic group, fluoroaliphatic
group, or aliphatic group in which the carbon number is equal to or less
than 10, and they may be different from one another or the same as others)
(7) A method of forming a thin film according to the above-mentioned
paragraph (6), wherein the silicon network polymer is made by reacting and
polymerizing organic metal compound represented by the following formulas
3 and/or 4 with at least one of alloy of alkali metals, copper and
magnesium.
##STR3##
(Where, R.sub.1, R.sub.2, R.sub.3 are aromatic group, fluoroaliphatic
group, or aliphatic group in which the carbon number is equal to or less
than 10, and they may be different from one another or the same as others)
(8) An electrically insulating thin film made by irradiating an
electromagnetic wave to the film of the silicon network polymer in the
presence of oxygen, thermally treating the thin film of silicon network
polymer at 200.degree. C. to 1,000.degree. C. in the presence of oxygen.
(9) A method of forming an electrically insulating thin film which
comprises the steps of: forming a thin film of silicon network polymer on
a substrate, irradiating an electromagnetic wave to the film of the
silicon network polymer in the presence of oxygen, and then thermally
treating the thin film of silicon network polymer at 200.degree. C. to
1,000.degree. C. in the presence of oxygen.
(10) A semiconductor device which uses the insulating layer as an
inter-layer insulating film, made by forming a thin film of silicon
network polymer on a substrate, irradiating an electromagnetic wave to the
film of the silicon network polymer in the presence of oxygen, and then
thermally treating the thin film of silicon network polymer at 200.degree.
C. to 1000.degree. C. in the presence of oxygen.
(11) A method of manufacturing a semiconductor device which uses an
insulating layer as an inter-layer insulating film, made by forming a thin
film of silicon network polymer on a substrate, irradiating an
electromagnetic wave to the thin film of the silicon network polymer in
the presence of oxygen, and then thermally treating the film of silicon
network polymer at 200.degree. C. to 1,000.degree. C. in the presence of
oxygen.
(12) A semiconductor device which uses the insulating layer flatten by a
chemical machinery polishing method as an inter-layer insulating film, in
which the insulating layer is made by forming a thin film of silicon
network polymer on a substrate, irradiating an electromagnetic wave to the
thin film of the silicon network polymer in the presence of oxygen, and
then thermally treating the thin film of silicon network polymer at
200.degree. C. to 1,000.degree. C. in the presence of oxygen.
(13) A method of manufacturing a semiconductor device which comprises a
step of flattening the insulating layer by a chemical machinery polishing
method, prepared by irradiating an electromagnetic wave to the thin film
of the silicon network polymer formed on a substrate in the presence of
oxygen, and then thermally treating the film of silicon network polymer at
200.degree. C. to 1,000.degree. C. in the presence of oxygen.
(14) A semiconductor device which uses the insulating layer as a conductive
layer and/or a semi-conductive layer, prepared by forming a thin film of
silicon network polymer on a substrate, irradiating an electromagnetic
wave to the film of the silicon network polymer in the presence of oxygen,
and then thermally treating the thin film of silicon network polymer at
200.degree. C. to 1000.degree. C. in the presence of oxygen.
(15) A method of manufacturing a semiconductor device wherein the
insulating layer is used as a conductive layer and/or a semi-conductive
layer, made by forming a thin film of silicon network polymer on a
substrate, irradiating an electromagnetic wave to the film of the silicon
network polymer in the presence of oxygen, and then thermally treating the
thin film of silicon network polymer at 200.degree. C. to 1,000.degree. C.
in the presence of oxygen.
The feature of the present invention is in that fine patterns are formed by
performing the irradiation of an electromagnetic wave and the heat
treatment using the material of which characteristics, for example, in
thermal resistance is changed by the irradiation of the electromagnetic
wave, without performing the wet etching or the dry etching as carried out
in the prior art. It is, further, possible to form a useful thin film by
using only heat treatment without irradiating the electromagnetic wave. In
case that network polysilane having fluoroalkyl group is used,
characteristics advantageous to improve the characteristics of a high
speed electronic device, because the dielectric constant of the insulating
film obtained becomes low. While the synthesis of the polysilane having
fluoroalkyl group is disclosed in Japanese Patent Application Laid-Open
No. 3-258834, the disclosure concerns straight chain polysilane, and thus
it is impossible to form fine patterns like the present invention. In
order to change the thermal resistance of a thin film by irradiating an
electromagnetic wave, it is necessary to use the silicon network polymer
according to the present invention in which photooxidation reaction,
photobridge reaction, photodecomposition reaction, etc., can be occurred.
The operation of the present invention will be explained hereinafter,
taking as an example of the photooxidation-bridging reaction of silicon
network polymer.
Silicon network polymer resolved into organic solvent such as toluene are
painted and dried on the substrate on which patterns are formed by using a
spin coating or dipping method to form a thin film with even thickness.
Next, an electromagnetic wave with wavelengths of 150 nm to 350 nm is
irradiated onto the thin film of silicon network polymer in the presence
of oxygen. Si--Si bonding of the polysilane structure in the thin film of
silicon network polymer is cut out at an irradiated area, and bonds to
oxygen to produce the structure containing many SiO skeletons. In this
process, the silicon network polymer of the present invention takes oxygen
into its molecular structure to expand in volume.
Then, the polymer is thermally treated at 200.degree. C. to 1,000.degree.
C. in a vacuum. The thin film of silicon network polymer at an unexposed
area is decomposed and volatilized from the substrate, or is thermally
decomposed to become a semi-conductive thin film such as SiC, amorphous
Si, etc. Because the silicon network polymer is thermally stable at a
heating temperature less than 200.degree. C., it is not decomposed and
converted into SiO, amorphous Si, etc.
Because at the exposed area the SiO with high thermal resistance has been
already formed, the SiO area remains on the substrate even after the heat
treatment. As a result, the negative pattern is formed. If the temperature
of the heat treatment for the substrate is more than 1,000.degree. C., the
SiO skeleton portion at the exposed area also is volatilized. Therefore,
no film remains on the substrate.
The inventors applied the same exposing and heating process as above to
straight chain polysilane. As a result, there was no polysilane film on
the substrate at both the exposed area and the unexposed area, after the
heat treatment. The reason lies in that the thermal resistance of straight
chain polysilane is low.
The heat stability of the silicon network polymer of the present invention
can be controlled by changing the formula ratio of the organic metal
compound represented by the formulas 1 and 2 in polymerization reaction.
As the formula ratio is increased, the heat stability becomes high. If it
is necessary to form no fine pattern, it is possible to abbreviated the
exposure process. Even if the silicon network polymer formed by
abbreviating the exposure process is thermally treated at 200.degree. C.
to 1,000.degree. C. in the presence of oxygen, an insulating film of which
the characteristic of electricity is excellent. Further, by oxydizing
silicon network polymer without heating it, irradiating light to it in the
presence of oxygen, it is possible to obtain an insulating film having an
improved characteristic in electricity. If necessary, both the
photoreaction and the thermal reaction can be used or either of them can
be used. The volume expansion due to oxidation reaction can be controlled
according to the stage of the process of the photo-oxidation reaction and
the thermal oxidation reaction and according to the stage of the process
of the thermal decomposition reaction of the organic group. Finally, it is
possible to eliminate the volume expansion of the thin film or occur the
volumetric shrinkage.
In case that the formed thin film is applied to a semiconductor device, a
mechanical characteristic of the thin film becomes very important. If the
film to be formed is shrunken in the process of forming, the tensile
stress is generated. Therefore, the formed film is fragile and is apt to
crack due to a small external force. While, If the film to be formed is
expanded in the process of forming, the compression stress is generated.
It is, therefore, hard to crack and extremely advantageous to work the
film.
Because the film containing many SiO skeletons according to the present
invention can control the volume expansion and the film stress generated
as described above, it is optimum to use in the manufacturing process of a
semiconductor device. It is desirable that in order to prevent a thin film
from cracking, it needs to expand the film in the process of forming, or
suppress the amount of shrinkage to the minimum amount. Because the thin
film of silicon network polymer according to the present invention is
excellent in a coating characteristic and a film characteristic, the
thickness of the film to be formed is not limited. If a thin film is
formed by using spin coating, it is easiest to obtain a thin film with
even thickness of 0.1 .mu.m to 1.0 .mu.m.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a GPC chart of poly (pentafluorophenylsilane) according to the
present invention.
FIG. 2 is a view of Raman spectrum of poly (pentafluorophenylsilane)
according to the present invention.
FIG. 3 is a view of visible ultraviolet absorption spectrum of poly
(pentafluorophenylsilane) according to the present invention.
FIG. 4 is a sectional view of an aluminum double-layer-wiring substrate
formed on a silicon wafer.
FIG. 5 is a view of infrared transmission spectra at the exposed area and
the unexposed area of a poly (phenylsilane) thin film, measured after
heating.
FIG. 6 is a graph showing the current-voltage characteristic of an n-type
silicon substrate/SiC thin film.
FIG. 7 is a view of far infrared transmission spectrum at the unexposed
area of a poly (n-propylsilane) thin film, measured after heating.
FIG. 8 is a graph showing the current-voltage characteristic of a p-n
junction of p-doped amorphous silicon of which the precursor body is an
n-type silicon and poly (n-propylsilane).
FIG. 9 is a sectional view of an aluminum double-layer-wiring substrate
formed on a silicon substrate.
BEST MORD FOR CARRING OUT THE INVENTION
Embodiments of the present invention will be explained
(Embodiment 1)
Tetrahydrafuran solution, 200 ml, of 0.4 mol of tetrachrolosilane and 0.4
mol of pentafluorobromobenzene was dropped into a nitrogen-converted flask
provided with a magnesium operation electrode and a pair of nickel
electrodes by using a dropping funnel, with ice-cooling. The Grignard
reaction of tetrachrolosilane and pentafluorobromobenzene was performed
under the circulating flow of solvent.
Reaction was performed at 0.degree. C. during 3 hours, with electric
potential scanning at 50 mV/sec between -3 V and 0 V applied between the
electrodes. The reacted solution is poured into methanol of 100 ml, and
re-precipitated and refined by using distilled water of 500 ml. The yield
was 51.3%.
The average molecular weight of polystylene conversion measured by GPC was
14,240.
FIG. 1 shows a GPC chart of the obtained poly (pentafluorophenylsilane),
and FIG. 2 shows Raman spectrum of the polymer. It is understood that the
spectrum of Si--Si bond is broad and networked. The ACS Symposium Series
579,408 (1994) discloses that the vibration spectrum of the networked
polysilane becomes broad.
FIG. 3 shows a visible ultraviolet absorption spectrum of the obtained
polymer. The absorption due to pentafluorophenyl group appears in the
neighborhood of 270 nm. In FIG. 3, graph a shows 1 m mol/l THF solution of
poly (pentasilane), and graph b shows 1 m mol/l THF solution of poly
(pentafluorophenylsilane).
Further, Table 1 shows the result of measurement of XPS (X-ray
Photoelectron Spectroscopy) the obtained polymer. Signals indicative of
fluorine, oxygen and carbon are observed. It is, therefore, understood
that the desired network polymer is obtained. Where, it seems that the
observed oxygen atom is introduced by the reaction with methanol when the
reaction is stopped.
TABLE 1
______________________________________
ATOM (ORBIT) RELATIVE INTENSITY
______________________________________
F (1s) 21.66
Si (2p) 6.20
C (1S) 61.29
O (1s) 10.85
______________________________________
(Embodiment 2)
Pentafluorobromobenzene is changed for nonafluoroiodobutane, and the
synthesis is carried out in the same way as Embodiment 1. As a result,
poly (nonafluorobutylsilane) was obtained with the yield of 55%.
(Embodiment 3)
Pentafluorobromobenzene is changed for heptafluoroiodopropane, and the
synthesis is carried out in the same way as Embodiment 1. As a result,
poly (heptafluoropropylsilane) was obtained with the yield of 50%.
(Embodiment 4)
Toluene solution of 20 wt % of the poly (pentafluorophenylsilane) obtained
in Embodiment 1 was spin-coated on a silicon wafer. After exposing it for
10 minutes by using 500 W mercury lamp in the presence of oxygen, the
thermal treatment is carried out for 1 hour at 500.degree. C. in a vacuum.
As a result, an insulating thin film with thickness of 1.5 .mu.m was
obtained.
We observed the insulating film by using a microscope and confirmed that
there is no crack due to the shrinkage of a thin film in the process of
heating, and that the formed film is very fine and uniform. The dielectric
constant of the film was 2.7, measured by using frequency of 1 kHz.
(Embodiment 5)
Toluene solution of 20 wt % of the poly (heptafluoropropylsilane) obtained
in Embodiment 3 was spin-coated on a silicon wafer. After exposing it for
10 minutes by using 500 W mercury lamp in the presence of oxygen, the
thermal treatment was carried out for 1 hour at 400.degree. C. in a
vacuum. As a result, an insulating thin film with thickness of 1.5 .mu.m
was obtained.
We observed the insulating film by using a microscope and confirmed that
there is no crack due to the shrinkage of a thin film in the process of
heating, and that the formed film is very fine and uniform. The dielectric
constant of the film was 2.5, measured by using frequency of 1 kHz.
(Embodiment 6)
Toluene solution of 30 wt % of the poly (pentafluorophenylsilane) obtained
in Embodiment 1 was spin-coated on a silicon wafer on which an aluminum
pattern (L/S=1 .mu.m and 1 .mu.m high) is formed, to form a film with
thickness of 2 .mu.m. After thermally treating the film for 1 hour at
400.degree. C. in an air, it was flattened in its surface by using a CMP
(Chemical Machinery Polishing) method.
There is no crack due to the polishing, and that the formed insulating film
is very strong. The withstand voltage was 700 V/.mu.m, and the dielectric
constant was 2.5.
FIG. 4 is a sectional view of an aluminum double-layer-wiring substrate
obtained by repeating the above-mentioned process.
Aluminum wiring 2 and aluminum pier 3 are formed by normally etching the
aluminum deposited by using a sputtering method. By forming the insulating
film 4 on the silicon wafer 1 on which active areas are formed, it is
possible to obtain an integrated circuit with high speed response.
(Embodiment 7)
After dropping the solution produced by dissolving 40 m mol of
trichrolophenylsilane (phenyl group is used instead of R.sub.1 in formula
3) to 5 ml of toluene, into the solution produced by adding 90 m mol of
metallic sodium to 4o ml of toluene heated to 110.degree. C. and agitating
and distributing it, the reaction is carried out for 1 hour. After cooling
the reacted solution, supernatant liquid obtained by eliminating insoluble
matters using a centrifugal separator is dropped into excessive methanol,
and re-precipitated and refined to obtain poly (phenylsilane). 20 wt % of
toluene solution of poly (phenylsilane) was spin-coated on a substrate.
After exposing it through a mask pattern for 10 minutes by using 500 W
mercury lamp in the presence of oxygen, the thermal treatment was carried
out for 1 hour at 700.degree. C. in a vacuum. As a result, a negative
pattern with the minimum L/S (line and space)=0.75 .mu.m was formed (the
thickness of the film is 1.5 .mu.m) at both the exposed area and the
unexposed area. We observed the negative pattern by using a microscope and
confirmed that there is no crack due to the shrinkage of a thin film in
the process of heating, and that the formed film is very fine and uniform.
FIG. 5 shows infrared transmission spectra at both the exposed area and the
unexposed area of the above-mentioned pattern. While at the exposed area a
signal of SiO in the neighborhood of 800 cm.sup.-1 is remarkable, at the
unexposed area a signal of SiC in the neighborhood of 800 cm.sup.-1 is
remarkable
(Embodiment 8)
An electrode is formed by spin-coating the poly (phenyl silane) in
Embodiment 7 on an n-type silicon substrate, thermally treating for lhour
at 700.degree. C. in a vacuum without exposure to light to form an SiC
thin film on an n-type silicon substrate, and evaporating gold onto the
SiC portion. Further, an indium electrode is formed on an n-type silicon
substrate. A bonding characteristic of the n-type silicon substrate/SiC
thin film is measured from an electric current/voltage curve obtained at
the electrodes. The results of measurement is shown in FIG. 6. by thermal
treatment of poly (phenylsilane), hetero-bonding of the n-type silicon
substrate and the SiC thin film having a rectifying characteristic was
formed easily.
(Embodiment 9)
20 wt % of toluene solution of poly (n-propylsilane) (n-propyl group is
used instead of R.sub.1 of formula 3) obtained in a way similar to that of
Embodiment 7 was spin-coated on a substrate. After exposing it through a
mask pattern by using a KrF excimer laser in a vacuum, thermal treatment
was carried out for 30 minutes at 350.degree. C. in a vacuum. As a result,
a positive pattern with the minimum L/S (line and space)=0.25 .mu.m was
formed (the thickness of the film is 0.1 .mu.m) at both the exposed area
and the unexposed area. It was seen that an amorphous silicon thin film is
formed at the unexposed area from the analysis of the far infrared
spectrum shown in FIG. 3.
(Embodiment 10)
After dropping the solution produced by dissolving 8 m mol of
trichrolopropylsilane (n-propyl group is used instead of R.sub.1 in
formula 3) and 32 m mol of dichrolopropylsilane (n-propyl groups were used
instead of R.sub.1, R.sub.2 and R.sub.3 in formula 3) to 5 ml of toluene,
into the solution produced by adding 90 m mol of metallic sodium to 4o ml
of toluene heated to 110.degree. C. and agitating and distributing it, the
reaction was carried out for 1 hour. After cooling the reacted solution,
supernatant liquid obtained by eliminating insoluble matters using a
centrifugal separator was dropped into excessive methanol, and
reprecipitated and refined to obtain poly (n-propylsilane). 20 wt % of
toluene solution of poly (n-propylsilane) was spin-coated on a substrate.
After exposing it through a mask pattern by using the KrF excimer laser in
the presence of oxygen, the thermal treatment was carried out for 1 hour
at 500.degree. C. in a vacuum.
As a result, a negative pattern of SiO.sub.2 with the minimum L/S (line and
space)=0.25 gm was formed (the thickness of the film is 1.5 .mu.m) at both
the exposed area and the unexposed area. We observed the negative pattern
by using a microscope and confirmed that there is no crack due to the
shrinkage of a thin film in the process of heating, and that the formed
film is very fine and uniform.
(Embodiment 11)
Toluene solution of 20 wt % of the same poly (n-propylsilane) as one
obtained in Embodiment 4 was spin-coated on an n-type silicon substrate to
form a poly (n-propylsilane) thin film. By thermally treating the film for
30 minutes at 400.degree. C. in a vacuum, it was converted into an
amorphous silicon thin film. By doping phosphorus into the amorphous
silicon thin film as the impurity, p-type amorphous silicon thin film was
formed. A p-n junction was formed by using the n-type silicon and p-type
amorphous silicon thin film, and the characteristic of the junction was
measured. The result of measurement is shown in FIG. 8.
(Embodiment 12)
Toluene solution of 30 wt % of the same poly (phenylsilane) as one in
Embodiment 7 was spin-coated on a silicon substrate 1 on which an aluminum
wiring 2 of L/S=1 .mu.m and 1 .mu.m high is formed, to form a film with
thickness of 2 .mu.tm. After thermally treating the film for 1 hour at
400.degree. C. in an air, it was flattened in its surface by using a CMP
(Chemical Machinery Polishing) method. There is no crack due to the
polishing, and that the formed insulating film 4 is very strong. The
withstand voltage for insulation was 600 V/.mu.m, and the dielectric
constant was 3.2.
FIG. 9 is a sectional view of an aluminum double-layer-wiring substrate
obtained by repeating the above-mentioned process. Aluminum wiring 2 and
aluminum pier 3 are formed by normally etching the aluminum deposited by
using a sputtering method. By forming the wiring on the silicon substrate
on which active areas are formed, it is possible to obtain an integrated
circuit.
New fluorosilicon network polymer of the present invention is excellent in
a coating characteristic and a film characteristic. It is, therefore,
possible to provide an electronic device with high performance and with
high speed response by using the polymer as an insulating film for
electronic devices.
By irradiating an electromagnetic wave and thermally treating after coating
a thin film of polysilane, it is possible to form easily and arbitrarily
the thin film having the functions of electrical conductivity (SiC),
semi-conductivity (a-Si), insulation (SiO.sub.2), light transmission
(SiO.sub.2), etc. It is, therefore, possible to perform easily the fine
work for a semiconductor, etc.
INDUSTRIAL APPLICABILITY
The present invention relates to silicon network polymer containing
fluorine in polymer structure, an insulating film and a manufacturing
method thereof.
The silicon network polymer containing fluorine in polymer structure is
useful for a method of forming a thin film by using a photolithography
method, a semiconductor device using the thin film or a method of
manufacturing the semiconductor device.
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